Conventional pumping machines that can be used for difficult-to-pump materials have displacement organs such as pistons, plungers, peristaltic hoses etc. However such displacement organs are subject to frictional wear and the drive of the machine is not properly isolated from the pumped material.
WO 2005/119063 discloses a hydraulically driven multicylinder diaphragm pumping machine, in particular for pumping difficult-to-pump materials. This pumping machine comprises a plurality of pump cylinders each having one end with an inlet and outlet for fluid to be pumped and another end with an inlet and outlet for hydraulic fluid. These inlets and outlets can be a separate inlet and outlet (for the hydraulic fluid) or a combined inlet/outlet (for the fluid material being pumped). The inlets and outlets are associated with respective inlet and outlet valves.
In such machine, a separator is located inside and is movable to-and-fro along each pump cylinder. The movable separator has one side facing the pumped-material end of the cylinder and another side facing the hydraulic-fluid end of the cylinder. This movable separator is connected to the inside of the pumped-material end of the cylinder by a first flexible diaphragm in the form of a concertina-like bellows that is expandable and contractable inside the cylinder along the length direction of the cylinder as the movable separator moves to-and-fro along the cylinder. The movable separator delimits a first chamber inside the first bellows-like flexible diaphragm for containing a variable volume of pumped fluid in communication via the inlet and outlet with a pumped fluid manifold and circuit. The movable separator is connected also to the inside of the second end of the cylinder by a second flexible diaphragm in the form of a concertina-like bellows that is contractable and expandable along the length direction of the cylinder in correspondence with expansion and contraction of the first flexible diaphragm. The second side of the movable separator delimits a second chamber inside the second expandable and contractable diaphragm for containing a variable volume of hydraulic fluid in communication with the second inlet and outlet. An annular space is defined between the outside of the first and second diaphragms and the inner wall of the pump cylinder which annular space in use contains a fluid that is the same as said hydraulic fluid or has similar hydraulic characteristics.
This pumping machine is directly driven by a hydraulic pump drive, greatly simplifying the machine and providing simple means of variation and control of the flow of the pumped fluid delivered. Moreover, the double diaphragm arrangement provides a double protection of the pumped fluid from the pumping fluid.
Further details of this pumping machine are described in WO 2005/119063 the contents whereof are incorporated herein by way of reference.
Supplemental research with such machines has demonstrated that various aspects such as the reliability of the operation of the bellows-like diaphragm could be improved.